XP 215s are very impressive for their size, (i own 4) but are too limited to be useful back up weapons in most games.
I had a non functional one, so i decided to to make it as potent as possible, I wasn't bothered if it was destroyed in the attempt.

Phase 1 - sticking to air pressure:

I replaced the faulty pump and attempted to deal with one of the 215s key weaknesses - the pinch trigger. I had a very broken XP 40 to hand and i manged to integrate its small pull valve, using a dremel to create the required space. I also added a new larger nozzle using the the conical front part of a pen to help focus the stream.

doing this allowed the blaster to be pumped to higher pressures that previously would have forced open the pinched tubing, dribbling water from the nozzle. I had some issues with the joins in my homemade internals not sealing at the higher pressures i wanted to use, i fixed this with more super glue over each join (not using epoxy as this was just test building and i wanted to easily be able to change things).

The higher pressure and now larger nozzle size allowed a range improvement from 7 to 8 meters. However useful shot time was very shot (1/2 a second or so) and too many pumps were required to reach suitable pressure again. I considered reducing the nozzle size but this would have rendered the blaster barely different to an unaltered one.

Phase 2 - CPS experimentation
I realized that air pressure wasn't going to achieve the performance that i wanted so i considered how i could convert it to CPS tech.
I considered a few designs but the following one allowed the most space for the bladder to expand:

To access the reservoir, I cut the front of it off (along the grey line in the concept image), when the blaster is re-assembled the cut is hidden by the shell. this allowed me to build in all the required tubing. I had some elastic exercise tubing to experiment with as the bladder.

Phase 3 - Results

After this initial construction the blaster was firing only 6m less than stock and the previous air pressure experiment. I opened it back up and managed to layer a second piece of the exercise tubing over the bladder. The current stats are:

*Currently the system retains the original air pump so must be charged by pumping underwater. it has no reservoir, just a pressure chamber.

I am really happy with the performance now, However the leaks have returned with the higher pressure of the double layer bladder and the previous quick fix of more super glue has not worked, I will need to figure out how to fix this (perhaps epoxy) before the blaster will be of any use a back up.

Wow, this is certainly very innovative. Never would have thought to try something like this.

Do you think you could get a good picture of what the shot looks like now?

Before the first Frozen Fury I did some modifications on our pistols (XP 40 specifically comes to mind). Nothing to this level but they increased the range and output. Was pretty fun. We fought in an abandoned theater with pistols.